It's my plesure.
Not at all.
You're welcome.
Don't mention it.
It doesn't matter.
It's nothing.
That's all right.
Never mind.
That's O.K.
It scarcely matters.
No matter.
Skip it.
It doesn't make any difference.
Forget it.
Not in the least.
It's of no consequence.
It doesn't matter a farthing.
No sweet.[美国俚语]